High-tensile, thin-wall differential threaded coupling

ABSTRACT

The disclosed embodiments include a differential coupling system, a method of coupling a first mandrel to a second mandrel and a coupler. In one embodiment, the system includes a first mandrel having a first external thread about an external surface of the first mandrel. The system also includes a second mandrel having a second external thread about an external surface of the second mandrel. The system further includes a coupler that includes a first internal thread that complements the first external thread of the first mandrel and a second internal thread that complements the second external thread of the second mandrel. The system further includes an aligning pin configured to engage a first aligning hole of the first mandrel and a second aligning hole of the second mandrel to restrict axial rotation between the first mandrel and the second mandrel when the first mandrel is engaged to the second mandrel.

BACKGROUND

The present disclosure relates to oil and gas exploration and production, and more particularly to a coupling subassembly for joining together tubing segments in a tool string.

Wells are drilled at various depths to access and produce oil, gas, minerals, and other naturally-occurring deposits from subterranean geological formations. Wells are also drilled in a variety of environments, including in deep water where ocean floor conditions may be softer or more unconsolidated. In such wells, drill strings and completion strings may extend to a variety of depths and may follow relatively circuitous paths to reach a location of a geological formation that is rich in extractable hydrocarbons.

To deploy tools at various locations and depths in the wellbore, a tool string, which may include a running tool, may be used to deploy tools or other devices. To form the tool string, tubing segments may be coupled together or with tooling subassemblies. These couplings may be achieved using coupling subassemblies that form robust, sealed joints between segments of tubing in a tool string. The coupling subassemblies also allow coupled tubing segments to disengage from each other.

BRIEF DESCRIPTION OF THE DRAWINGS

The following figures are included to illustrate certain aspects of the present disclosure, and should not be viewed as exclusive embodiments. The subject matter disclosed is capable of considerable modifications, alterations, combinations, and equivalents in form and function, without departing from the scope of this disclosure.

FIG. 1A illustrates a schematic view of an off-shore well in which a tool string is deployed according to an illustrative embodiment;

FIG. 1B illustrates a schematic view of an on-shore well in which a tool string is deployed according to an illustrative embodiment;

FIG. 2 illustrates a schematic, cross-section view of a coupling assembly for joining two segments of tubing together, in accordance with an illustrative embodiment;

FIG. 3 illustrates a perspective view of a portion of an embodiment of a coupling used in the coupling assembly of FIG. 2;

FIG. 4A illustrates a perspective view of a portion of an embodiment of a first mandrel used in the coupling assembly of FIG. 2;

FIG. 4B illustrates a perspective view of a portion of an embodiment of a second mandrel used in the coupling assembly of FIG. 2;

FIG. 5A illustrates a cross-section view of a portion of a first external thread of the first mandrel of FIG. 4A engaged to a first internal thread of the coupler of FIG. 3;

FIG. 5B illustrates a cross-section view of a portion of a second external thread of the second mandrel of FIG. 4B engaged to a second internal thread of the coupler of FIG. 3; and

FIG. 6 illustrates a perspective view of the coupling assembly of FIG. 2 that includes the coupler of FIG. 3, the first mandrel of FIG. 4A, and the second mandrel of FIG. 4B.

The illustrated figures are only exemplary and are not intended to assert or imply any limitation with regard to the environment, architecture, design, or process in which different embodiments may be implemented.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

In the following detailed description of the illustrative embodiments, reference is made to the accompanying drawings that form a part hereof These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is understood that other embodiments may be utilized and that logical structural, mechanical, electrical, and chemical changes may be made without departing from the spirit or scope of the invention. To avoid detail not necessary to enable those skilled in the art to practice the embodiments described herein, the description may omit certain information known to those skilled in the art. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the illustrative embodiments is defined only by the appended claims.

Liner hanger systems and other types of tool strings may be used during well construction or well remediation and repair in locations ranging from just below the wellhead system to locations deep within a well. Tool strings used in such systems may therefore be extendable, and may include couplings that are tolerant of bending and vibration induced forces to resist decoupling within the wellbore. In particular, tool strings, such as Drill String Testing (DST) strings, that deploy running tools used to place or set downhole equipment, such as liner hangers, plugs or packers, may be resistant to such induced forces to maintain the integrity of the tool string and prevent the loss of the tool in the well. Tool strings that deploy other types of tools may be similarly resistant to such induced forces.

Some tool strings may include coupling assemblies where tubing segments are joined together by couplers to extend the tool string further into a formation. The present disclosure relates to a coupling assembly that tolerates the static and dynamic loads experienced by the tool string and prevents the tool string from decoupling due to hoop stress, vibration, torsion, and other forces that may be experienced when the tool string is rotated and/or manipulated in a well. The coupling assembly is also operable to withstand additional loads, which may result from non-conventional or unanticipated loading of threaded interfaces when the assembly is navigating a tight radius in the well. In some embodiments, the coupling assembly is used in a Landing String of a (DST string. In one of such embodiments, the coupling assembly is installed on an ocean floor subsea equipment such as a blowout preventer (BOP) to provide for disconnection and isolation of tubing pressure in case of a required ocean floor disconnect during the DST operations. In another one of such embodiments, the coupling assembly is installed on DST tools positioned further downhole from the ocean floor. In further embodiments, the coupling assembly is used to couple tubing segments in any suitable tool string, including, for example, a running tool for deploying a liner hanger.

Turning now to the figures, FIG. 1A illustrates a schematic view of an offshore platform 142 operating a tool string 128 that includes a coupling assembly 100 according to an illustrative embodiment. The coupling assembly 100 in FIG. 1A may be deployed to couple sections of a subsea test tree residing in a blowout preventer 139 or to couple segments of the tool string 128 in a sub-sea well 138 accessed by the offshore platform 142. As defined herein, the “offshore platform” 142 may be a floating platform, a platform anchored to a seabed 140 or a vessel.

Alternatively, FIG. 1B illustrates a schematic view of a rig 104 in which a tool string 128 is deployed that includes a coupling assembly 100 in accordance with an illustrative embodiment. The rig 104 is positioned at a surface 124 of a well 102. The well 102 includes a wellbore 130 that extends from the surface 124 of the well 102 to a subterranean substrate or formation 134. The well 102 and the rig 104 are illustrated onshore in FIG. 1B.

FIGS. 1A-1B each illustrate possible uses or deployments of the coupling assembly 100, which in either instance may be used in tool string 128 to deploy a tool 144 or other device downhole. In the embodiments illustrated in FIG. 1A and 1B, the wellbore 130 has been formed by a drilling process in which dirt, rock and other subterranean material has been cut from the formation 134 by a drill bit operated via a drill string to create the wellbore 130. During or after the drilling process, a portion of the wellbore may be cased with a casing (not illustrated in FIGS. 1A and 1B). In other embodiments, the wellbore may be maintained in an open-hole configuration without casing.

The tool string 128 may include sections of tubing, each of which are joined to adjacent tubing by threaded or other connection types, such as coupling assembly 100. The tool string 128 may refer to the collection of pipes, mandrels or tubes as a single component, or alternatively to the individual pipes, mandrels, or tubes that comprise the string. The term tool string is not meant to be limiting in nature and may include a running tool or any other type of tool string used to deploy the tool 144 or equipment in the wellbore. In some embodiments, the tool string 128 may include a passage disposed longitudinally in the tool string 128 that is capable of allowing fluid communication between the surface 124 of the well 102 and a downhole location 136. It is noted that the coupling assembly 100 described herein may be used to couple tubing segments in any suitable tool string, including, for example, a running tool for deploying a liner hanger.

The lowering of the tool string 128 may be accomplished by a lift assembly 106 associated with a derrick 114 positioned on or adjacent to the rig 104 or offshore platform 142. The lift assembly 106 may include a hook 110, a cable 108, a traveling block (not shown), and a hoist (not shown) that cooperatively work together to lift or lower a swivel 116 that is coupled an upper end of the tool string 128. The tool string 128 may be raised or lowered as needed to add additional sections of tubing to the tool string 128 to position the distal end of the tool string 128 at the downhole location 136 in the wellbore 130.

An illustrative embodiment of a coupling assembly 100 that may be used to couple together tubing segments in a tool string is described in more detail with regard to FIGS. 2-6. Each coupling assembly 100 includes a first mandrel 204 and a second mandrel 206 joined by a coupler 202 at a first end 230 of the first mandrel 204 and a second end 232 of the second mandrel 206. Each mandrel may form a portion of a segment of a tool string.

The coupler 202 includes a threaded interface about an internal surface of the coupler 202 to engage the first mandrel 204 and second mandrel 206. In an embodiment, the coupler 202 includes a first internal thread 210 on a first end 236 of the coupler 202 and a second internal thread 212 on a second end 238 of the coupler 202. The first internal thread 210 engages a first external thread 218 of the first mandrel 204 and the second internal thread 212 engages a second external thread 226 of the second mandrel 206.

In some embodiments, the first internal thread 210 and the second internal thread 212 have different thread pitches. In such embodiments, the first external thread 218 is complementary to and engages the first internal thread 210 and the second external thread 226 is complementary to and engages the second internal thread 212.

One or more aligning pins 216 are inserted into first mandrel aligning holes 219 and second mandrel aligning holes 217. In the embodiment illustrated in FIG. 2, the aligning pin 216 is an aligning pin that is configured to engage a first mandrel aligning hole 219 and a second mandrel aligning hole 217 to align the first mandrel 204 with respect to the second mandrel 206, and to restrict axial movement of the first mandrel 204 with respect to the second mandrel 206 once the first mandrel 204 and second mandrel 206 are engaged. In some embodiments, the coupling assembly 100 further includes one or more port interfaces 220. Each port interface 220 couples a first conduit 221 of the first mandrel 204 to a second conduit 222 of the second mandrel. The first conduit 221 and second conduit 222 may be a hydraulic conduit, wire conduit, or other suitable conduit for conveying a hydraulic or electrical line, such as a control line. The port interface may be an interface of a male connector of the first conduit 221 coupled to a female connector of the second conduit 222, or vise versa. In such embodiments, the port interface 220 forms an electrical or hydraulic coupling between the first mandrel 204 and second mandrel 206.

In some embodiments, the coupling assembly 100 further includes a locking mechanism 240, such as a locknut, positioned adjacent to the first end 236 or the second end 238 of the coupler 202. The locking mechanism 240 has a threaded interface 242 to engage the first mandrel 204 or second mandrel 206 and to prevent longitudinal motion of the coupler 202 with respect to the first mandrel 204 or the second mandrel 206. In one of such embodiments, multiple locking mechanisms (not shown) are positioned adjacent to both the first end 236 and the second end 238 of the coupler 202 to secure the coupler 202 and to prevent longitudinal motion of with respect to the first or the second mandrels 204 and 206.

FIG. 3 shows a portion of an exemplary coupler 202 used in the coupling assembly 100. The coupler 202 includes the first internal thread 210, which is configured to engage the first external thread 218 of the first mandrel 204, and the second internal thread 212, which is configured to engage the second external thread 226 of the second mandrel 206. The coupler 202 also includes a plurality of visual indicators 265 that indicate the position of the coupler 202 with respect to the first mandrel 204 and second mandrel 206. In some embodiments, the first mandrel 204 and second mandrel 206 also include visual indicators, which when aligned with the visual indicators 265 of the coupler 202, indicate that the first mandrel 204 and second mandrel 206 are aligned with each other. The coupler 202 also includes a window 260. The window 260 may be a radial slot that is either open or filled with a transparent material to allow an operator to visually inspect the area surrounded by the coupler 202 to determine whether the first mandrel 204 and second mandrel 206 are aligned.

FIG. 4A shows an embodiment of a first end 230 of the first mandrel 204, as shown in the coupling assembly 100 of FIG. 2. The first end 230 includes the first external thread 218 for engaging the first internal thread 210 of the coupler 202. The first end 230 also includes the openings of the first conduits 221 having port interfaces 220 and first mandrel aligning holes 219 for receiving aligning pins 216. The first end 230 also includes a first visual indicator 266. The first conduits 221 and first mandrel aligning holes 219 are positioned about the periphery of the first mandrel to provide a desired number of aligning interfaces and port interfaces 220.

The first visual indicator 266 may be a milled, etched, painted, or otherwise marked radial line, on the outer surface of the first mandrel 204 at a first, predetermined distance from the first end 230 of the first mandrel 204. In the embodiment of FIG. 4A, the first visual indicator 266 marks the position of aligning pin 216 and provides a means to identify a location of the aligning pin 216 when the first mandrel 204 is engaged to the coupler 202 and the aligning pin 216 hidden from view by the coupler 202.

FIG. 4B shows an embodiment of a second mandrel 206, as shown in the coupling assembly 100 of FIG. 2, and more particularly, a second end 232 of the second mandrel 206. The second end 232 of the second mandrel 206 includes the second external thread 226 for engaging the second internal thread 212 of the coupler 202. The second end 232 also includes the openings of the second conduits 222 having port interfaces 220 and second mandrel aligning holes 217 for receiving aligning pins 216. The second end 232 also includes a second visual indicator 267. The second conduits 222 and second mandrel aligning holes 217 are positioned about the periphery of the second mandrel 206 to provide a desired number of aligning interfaces and port interfaces 220.

The second visual indicator 267, similar to the first visual indicator 266, may be a milled, etched, painted, or otherwise marked radial line, on the outer surface of the second mandrel 206 at a first, predetermined distance from the second end 232 of the second mandrel 206. In some embodiments, the second visual indicator 267 provides a visual indication of a location of one of the second mandrel aligning holes 217 of the second mandrel 206. In other embodiments, the first and second visual indicators 266 and 267 provide a visual indication that the first mandrel 204 and second mandrel 206 are aligned. As such, the first and second visual indicators 266 and 267 provide readily identifiable alignment indications even when view of the aligning pins 216 and port interfaces 220 are hidden from view by the coupler 202.

FIG. 5A illustrates a cross-section view of the first external thread 218 of the first mandrel 204 of FIG. 4A engaged to the first internal thread 210 of the coupler 202 of FIG. 3. FIG. 5B illustrates a cross-section view of a portion of a second external thread 226 of the second mandrel 206 of FIG. 4B engaged to a second internal thread of the coupler of FIG. 3. In the embodiment illustrated in FIG. 5A, the first internal thread 210 and first external thread 218 have a thread pitch that is greater than the thread pitch of the second internal thread 212 and second external thread 226. For example, the first internal thread 210 and first external thread 218 may have a thread pitch of approximately three threads per inch while the second internal thread 212 and second external thread 226 may have a thread pitch of approximately two threads per inch. In such an embodiment, turning of the coupler 202 would result in the he second internal thread 212 and second external thread 226 advancing (along a longitudinal axis of the coupler 202) at approximately 1.5 times the rate of retreat of the first internal thread 210 and the first external thread 218.

In the embodiment illustrated in FIGS. 5A and 5B, the first external thread 218 and the second external thread 226 have a reverse lead angle α, which may be, for example, negative seven degrees taken from a base line that is perpendicular to the longitudinal axis of the first mandrel 204 or second mandrel 206. The negative flank angle results in the coupler 202 being drawn inward to compress the coupling assembly 100 when an axial tensile load is applied to the coupling assembly 100 through a tool string that includes the assembly. Further, the first external thread 218 and second external thread may have a trailing flank angle of θ, which may be, for example, approximately forty-five degrees. This configuration directs loads generated from axial loads experienced at the coupling of the first and second external threads 218 and 226 with the first and second internal threads 210 and 212 inwards and towards the longitudinal axis of the first mandrel 204 and second mandrel 206, respectively. In other embodiments, the first and second external threads have a reverse lead angle α of approximately negative three to negative thirty degrees and a trailing flank angle θ of approximately thirty to sixty degrees to accommodate a variety of factors such as the tensile load of the first mandrel 204 and second mandrel 206, the length of the coupler 202, the thread pitch and thread profile of the external and internal threads 218, 226, 210, and 212, and the material composition of the first mandrel 204 and second mandrel 206 and the coupler 202.

An illustrative method of assembling the foregoing parts of the coupling assembly 100 is described with regard to FIG. 6. The method includes axially aligning the first end 230 of the first mandrel 204 with the second end 232 of the second mandrel 206. This first and second ends 230 and 232 may be axially aligned by aligning the first visual indicator 266 with the second visual indicator 267. Once the first mandrel 204 and second mandrel 206 are axially aligned with each other, the first mandrel 204 and second mandrel 206 are then held in place to prevent axial motion. The method also includes threading the first internal thread 210 of the coupler 202 onto the first external thread 218 of the first mandrel 204 to engage the first end 230 of the first mandrel 204 with the first end 236 of the coupler 202. The rate at which the first mandrel 204 engages with and disengages from the coupler 202 at a first engagement rate that is based on the thread pitch of the first external thread 218 and first internal thread 210.

The second internal thread 212 of the coupler 202 is then threaded to the second external thread 226 of the second mandrel 206 to engage the second end 232 of the second mandrel 206 with the second end 238 of the coupler 202. Given that the first mandrel 204 is already engaged to the coupler 202, threading the coupler 202 to the second mandrel 206 causes the first mandrel 204 to disengage from the coupler 202 at the first engagement rate.

The differential pitch between the first internal thread 210 and second internal thread 212, however, induces the second mandrel 206 to axially engage the coupler 202 at a second engagement rate that is different than the first engagement rate (or disengagement rate of the first mandrel 204). For example, if the pitch of the first internal thread 210 and first external thread 218 is approximately three threads per inch while the thread pitch of the second internal thread 212 and second external thread 226 is approximately two threads per inch, then the coupler 202 will engage the second mandrel 206 approximately fifty percent faster than the coupler 202 will disengage from the first mandrel 204, thereby resulting in the first mandrel 204 moving toward the second mandrel 206 if the coupler 202 is turned while the first mandrel 204 and second mandrel 206 are constrained from rotating. In an embodiment, the first mandrel 204 and second mandrel 206 are constrained from rotating relative to one another by aligning pins 216.

The foregoing method induces the second mandrel 206 to move towards the first mandrel 204 until the first end 230 of the first mandrel 204 is engaged to the second end 232 of the second mandrel 206. The method may further include visually or optically inspecting the interface between the first mandrel 204 and second mandrel via the window 260 to determine if the first mandrel 204 is aligned with the second mandrel 206.

The above-disclosed embodiments have been presented for purposes of illustration and to enable one of ordinary skill in the art to practice the disclosure, but the disclosure is not intended to be exhaustive or limited to the forms disclosed. Many insubstantial modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the disclosure. For instance, although the flowcharts depict a serial process, some of the steps/processes may be performed in parallel or out of sequence, or combined into a single step/process. The scope of the claims is intended to broadly cover the disclosed embodiments and any such modification. Further, the following clauses represent additional embodiments of the disclosure and should be considered within the scope of the disclosure:

Clause 1, a differential threaded coupling system comprising: a first mandrel having a first external thread about an external surface of the first mandrel; a second mandrel having a second external thread about an external surface of the second mandrel; a coupler comprising a first internal thread that complements the first external thread of the first mandrel and a second internal thread that complements the second external thread of the second mandrel; and an aligning pin configured to engage a first aligning hole of the first mandrel and a second aligning hole of the second mandrel to restrict axial rotation between the first mandrel and the second mandrel when the first mandrel is engaged to the second mandrel.

Clause 2, the coupling system of clause 1, wherein each tooth of the first external thread and second external thread has a reverse lead flank angle of approximately −3 to −30 degrees and a trailing flank angle of approximately 30 to 60 degrees.

Clause 3, the coupling system of clause 2, wherein the reverse lead angle is approximately −7 degrees and the trailing flank angle is approximately 45 degrees.

Clause 4, the coupling system of any of clauses 1-3, wherein the first external thread and first internal thread have a first thread pitch and the second internal thread and second external thread have a second thread pitch, the second thread pitch being less than the first thread pitch, such that rotation of the coupler results in an engagement rate of the coupler to the second mandrel that is greater than a disengagement rate of the coupler to the first mandrel.

Clause 5, the coupling system of any of clauses 1-4, further comprising a plurality of port interfaces, each port interface forming a coupling between a first conduit of the first mandrel and a second conduit of the second mandrel.

Clause 6, the coupling system of any of clauses 1-5, wherein the plurality of port interfaces comprises an electrical connector, and wherein the electrical connector is coupled to a first conduit comprising an electrical conduit, and a second conduit comprising an electrical conduit.

Clause 7, the coupling system of any of clauses 1-6, wherein the plurality of port interfaces comprises a hydraulic connector, and wherein the hydraulic connector is coupled to a first conduit comprising a fluid conduit, and a second conduit comprising a fluid conduit.

Clause 8, the coupling system of any of clauses 1-7, wherein the coupler comprises a window for viewing the first mandrel and second mandrel when the first and second mandrels are coupled to the coupler.

Clause 9, a method of coupling a first mandrel to a second mandrel, the method comprising: aligning a first end of a first mandrel to a second end of a second mandrel, the first mandrel having a first external thread about an external surface of the first mandrel and the second mandrel having a second external thread about an external surface of the second mandrel; threading a coupler to the first mandrel to engage a first internal thread of the coupler to the first external thread of the first mandrel, wherein the first internal thread and first external thread have a first thread pitch; threading the coupler to the second mandrel to engage a second internal thread of the coupler to the second external thread of the second mandrel, wherein the second internal thread and second external thread have a second thread pitch, wherein the second thread pitch is less than the first thread pitch, such that rotating the coupler relative to the first mandrel and second mandrel simultaneously results in the coupler engaging the second mandrel at a faster rate than the coupler disengages the first mandrel, and the second mandrel being drawn towards the first mandrel until the first end of the first mandrel engages the second end of the second mandrel.

Clause 10, the method of clause 9, wherein aligning the first end of the first mandrel to the second end of the second mandrel comprises aligning an aligning pin with a first aligning hole of the first mandrel and a second aligning hole of the second mandrel, wherein the aligning pin is configured to restrict axial rotation between the first mandrel and the second mandrel when the first mandrel is engaged to the second mandrel.

Clause 11, the method of any of clauses 9 and 10, wherein aligning the first end of the first mandrel to the second end of the second mandrel comprises aligning a plurality of port interfaces, the method further comprising coupling a first conduit of the first mandrel to a second conduit of the second mandrel at each of the plurality of port interfaces.

Clause 12, the method of any of clauses 9-11, wherein the plurality of port interfaces comprises an electrical connector, and wherein each electrical connector is coupled to a first conduit comprising an electrical conduit, and a second conduit comprising an electrical conduit.

Clause 13, the method of any of clauses 9-12, wherein the plurality of port interfaces comprises a hydraulic connector, and wherein each hydraulic connector is coupled to a first conduit comprising a fluid conduit, and a second conduit comprising a fluid conduit.

Clause 14, the method of any of clauses 9-13, further comprising aligning a first visual indicator of the first mandrel to a second visual indicator of the second mandrel to align the first end of the first mandrel to the second end of the second mandrel.

Clause 15, the method of any of clauses 9-14, further comprising visually determining if the first end of the first mandrel is aligned with the second end of the second mandrel by observing the first mandrel and second mandrel through a window of the coupler.

Clause 16, the method of any of clauses 9-15, wherein each of the first external thread and second external thread has a reverse lead flank angle of approximately −3 to −30 degrees and a trailing flank angle of approximately 30 to 60 degrees.

Clause 17, the method of clause 16, wherein the reverse lead angle is approximately −7 degrees and the trailing flank angle is approximately 45 degrees.

Clause 18, a coupler comprising: a cavity having a first end for receiving a first mandrel and a second end for receiving a second mandrel; a first internal thread at the first end, the first internal thread having a thread profile that complements a first external thread of the first mandrel, wherein the first internal thread and first external thread have a first thread pitch; and a second internal thread having a thread profile that complements a second external thread of the second mandrel, wherein the second internal thread and second external thread have a second thread pitch, the second thread pitch being less than the first thread pitch such that rotating the coupler relative to the first mandrel and second mandrel simultaneously results in the coupler engaging the second mandrel at a faster rate than the coupler disengages the first mandrel.

Clause 19, the coupler of clause 18, further comprising a window to provide a view of the first mandrel and second mandrel when the first mandrel and second mandrel are engaged by the coupler.

Clause 20, the coupler of any of clauses 18 and 19, further comprising at least one visual indicator indicative of a rotational position of the coupler with respect to at least one of the first mandrel and the second mandrel.

Unless otherwise specified, any use of any form of the terms “connect,” “engage,” “couple,” “attach,” or any other term describing an interaction between elements in the foregoing disclosure is not meant to limit the interaction to direct interaction between the elements and may also include indirect interaction between the elements described. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Unless otherwise indicated, as used throughout this document, “or” does not require mutual exclusivity. It will be further understood that the terms “comprise” and/or “comprising,” when used in this specification and/or the claims, specify the presence of stated features, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof. In addition, the steps and components described in the above embodiments and figures are merely illustrative and do not imply that any particular step or component is a requirement of a claimed embodiment.

It should be apparent from the foregoing that embodiments of an invention having significant advantages have been provided. While the embodiments are shown in only a few forms, the embodiments are not limited but are susceptible to various changes and modifications without departing from the spirit thereof. 

We claim:
 1. A differential threaded coupling system comprising: a first mandrel having a first external thread about an external surface of the first mandrel; a second mandrel having a second external thread about an external surface of the second mandrel; a coupler comprising a first internal thread that complements the first external thread of the first mandrel and a second internal thread that complements the second external thread of the second mandrel; and an aligning pin configured to engage a first aligning hole of the first mandrel and a second aligning hole of the second mandrel to restrict axial rotation between the first mandrel and the second mandrel when the first mandrel is engaged to the second mandrel.
 2. The system of claim 1, wherein each tooth of the first external thread and second external thread has a reverse lead flank angle of approximately −3 to −30 degrees and a trailing flank angle of approximately 30 to 60 degrees.
 3. The system of claim 2, wherein the reverse lead angle is approximately −7 degrees and the trailing flank angle is approximately 45 degrees.
 4. The system of claim 1, wherein the first external thread and first internal thread have a first thread pitch and the second internal thread and second external thread have a second thread pitch, the second thread pitch being less than the first thread pitch, such that rotation of the coupler results in an engagement rate of the coupler to the second mandrel that is greater than a disengagement rate of the coupler to the first mandrel.
 5. The system of claim 1, wherein the coupler comprises a window for viewing the first mandrel and second mandrel when the first and second mandrels are coupled to the coupler.
 6. The system of claim 1, further comprising a plurality of port interfaces, each port interface forming a coupling between a first conduit of the first mandrel and a second conduit of the second mandrel.
 7. The system of claim of claim 6, wherein the plurality of port interfaces comprises an electrical connector, and wherein the electrical connector is coupled to a first conduit comprising an electrical conduit, and a second conduit comprising an electrical conduit.
 8. The system of claim of claim 6, wherein the plurality of port interfaces comprises a hydraulic connector, and wherein the hydraulic connector is coupled to a first conduit comprising a fluid conduit, and a second conduit comprising a fluid conduit.
 9. A method of coupling a first mandrel to a second mandrel, the method comprising: aligning a first end of a first mandrel to a second end of a second mandrel, the first mandrel having a first external thread about an external surface of the first mandrel and the second mandrel having a second external thread about an external surface of the second mandrel; threading a coupler to the first mandrel to engage a first internal thread of the coupler to the first external thread of the first mandrel, wherein the first internal thread and first external thread have a first thread pitch; and threading the coupler to the second mandrel to engage a second internal thread of the coupler to the second external thread of the second mandrel, wherein the second internal thread and second external thread have a second thread pitch, wherein the second thread pitch is less than the first thread pitch, such that rotating the coupler relative to the first mandrel and second mandrel simultaneously results in the coupler engaging the second mandrel at a faster rate than the coupler disengages the first mandrel, and the second mandrel being drawn towards the first mandrel until the first end of the first mandrel engages the second end of the second mandrel.
 10. The method of claim 9, wherein aligning the first end of the first mandrel to the second end of the second mandrel comprises aligning an aligning pin with a first aligning hole of the first mandrel and a second aligning hole of the second mandrel, wherein the aligning pin is configured to restrict axial rotation between the first mandrel and the second mandrel when the first mandrel is engaged to the second mandrel.
 11. The method of claim 9, wherein aligning the first end of the first mandrel to the second end of the second mandrel comprises aligning a plurality of port interfaces, the method further comprising coupling a first conduit of the first mandrel to a second conduit of the second mandrel at each of the plurality of port interfaces.
 12. The method of claim 11, wherein the plurality of port interfaces comprises an electrical connector, and wherein each electrical connector is coupled to a first conduit comprising an electrical conduit, and a second conduit comprising an electrical conduit.
 13. The method of claim 11, wherein the plurality of port interfaces comprises a hydraulic connector, and wherein each hydraulic connector is coupled to a first conduit comprising a fluid conduit, and a second conduit comprising a fluid conduit.
 14. The method of claim 9, further comprising aligning a first visual indicator of the first mandrel to a second visual indicator of the second mandrel to align the first end of the first mandrel to the second end of the second mandrel.
 15. The method of claim 14, further comprising visually determining if the first end of the first mandrel is aligned with the second end of the second mandrel by observing the first mandrel and second mandrel through a window of the coupler.
 16. The method of claim 9, wherein each of the first external thread and second external thread has a reverse lead flank angle of approximately −3 to −30 degrees and a trailing flank angle of approximately 30 to 60 degrees.
 17. The method of claim 16, wherein the reverse lead angle is approximately −7 degrees and the trailing flank angle is approximately 45 degrees.
 18. A coupler comprising: a cavity having a first end for receiving a first mandrel and a second end for receiving a second mandrel; a first internal thread at the first end, the first internal thread having a thread profile that complements a first external thread of the first mandrel, wherein the first internal thread and first external thread have a first thread pitch; and a second internal thread having a thread profile that complements a second external thread of the second mandrel, wherein the second internal thread and second external thread have a second thread pitch, the second thread pitch being less than the first thread pitch such that rotating the coupler relative to the first mandrel and second mandrel simultaneously results in the coupler engaging the second mandrel at a faster rate than the coupler disengages the first mandrel.
 19. The coupler of claim 18, further comprising a window to provide a view of the first mandrel and second mandrel when the first mandrel and second mandrel are engaged by the coupler.
 20. The coupler of claim 18, further comprising at least one visual indicator indicative of a rotational position of the coupler with respect to at least one of the first mandrel and the second mandrel. 